1. Field of the Invention:
This invention relates to a method of operating a copper converter in which crude copper is produced from matte.
2. Description of the Prior Art:
A copper converter is a furnace for producing crude copper from matte by oxidizing the matte and removing iron and sulfur therefrom by the air of oxygen-enriched air blown thereinto through the tuyeres located below the surface of the molten charge. Its operation includes a stage of slag forming and a stage of blister forming. During the stage of slag forming, FeS is oxidized into FeO, and sulfur is oxidized into SO.sub.2 and exhausted. If FeO is oxidized, it forms Fe.sub.3 O.sub.4. As the high melting point and viscosity of Fe.sub.3 O.sub.4 affects the furnace operation adversely, a flux, such as solid silica, is introduced into the furnace so that SiO.sub.2 in the flux may combine with FeO to form an iron-silicate slag. The removal of the iron-silicate slag completes the stage of slag forming. The molten charge is further oxidized to produce crude copper as a result of reactions including those represented by the equations (1) and (2) EQU Cu.sub.2 S+O.sub.2 =2Cu+SO.sub.2 ( 1) EQU Cu.sub.2 S+2CU.sub.2 O=6Cu+SO.sub.2 ( 2)
during the stage of blister forming. As all of the reactions taking place during the two stages are exothermic, the molten charge is raised to so high a temperature that the brick lining of the furnace may be damaged. Therefore, it is usual to introduce a cold charge into the furnace to appropriately control the temperature of the molten charge. It is usual to use copper scrap, or smoke particles rising from a copper smelting operation, as a cold charge.
The flux and the cold charge are usually introduced intermittently by a conveyor, or the like in a chute extending through an exhaust gas hood during blowing through the top opening of the converter. Sometimes, however, they are supplied from a container suspended by a crane into the top opening of the converter before the blowing is started.
If the flux and the cold charge are supplied through the top opening of the converter, however, they gather directly below the top opening and partly float on the surface of the molten charge. Therefore, they require a lot of time for melting and reacting, resulting in a lack of uniformity in the temperature of the molten charge. Those portions of the molten charge which have a relatively high temperature damage the brick lining. The molten charge portions having a relatively low temperature have a higher viscosity, which gives rise to increased splashing.
If the flux and the cold charge are, on the other hand, introduced during the blowing, a large amount of air is drawn into the exhaust gas hood for the converter as the chute establishes fluid communication between the exhaust gas hood and the exterior of the converter. The air drawn into the hood lowers the concentration of SO.sub.2 in the exhaust gas and thereby adversely affects the operation of a sulfuric acid plant. If, on the contrary, a positive pressure is built up in the hood for some reason for other, the smoke leaking therefrom presents the problem of environmental pollution. In order to avoid these problems as far as possible, it is imperative to introduce large quantities of flux and cold charge within a short time. This, however, results in a shape drop of molten charge temperature and therefore a great increase of splashing.
As a powdery cold charge, such as smoke particles, is scattered by the gas rising through the top opening of the converter, it is usual to agglomerate it into pellets, or the like, It is, however, impossible to avoid a certain loss of the material due to its powdering during its transportation. Although the scattering material is collected for reuse by a dust collector or like device, it is definitely true that the converter has a correspondingly low production yield, and that the particles are not easy to handle and their scattering is very likely to worsen the problem of environmental pollution.